Hello,

My data is organized in a worksheet like this:

1 jan | 2 jan | 3 jan | 4 jan | 5 jan | 6 jan | 7 jan | 8 jan | 9 jan
| 10 jan | 11 jan | 12 jan | 13 jan | 14 jan | etc.
| | | | | |
| | X | X | | | X
| | etc

So, in the first row, dates are stated and in the second row data is
filled. Now I want to count the blanks per week, so the result will be
a table like this:

week 1 | week 2 | week 3 | etc.
7 | 4 | 6 | etc.

Using the formula COUNTBLANK(A1:A7) doesn't seem to be the solution,
because dragging this formula to the right leads to COUNTBLANK(A2:A8)
instead of the correct calculation COUNTBLANK(A8:A14).
Can somebody help me with the correct formula?

Thanks!